Bisphenol A is prepared by reacting an excess amount of phenol with acetone in the presence of an acid catalyst. In order to obtain high purity bisphenol A from this reaction product, low-boiling substances including water are removed and solid addition product crystals of bispenol A and/or bisphenol A and phenol are precipitated by crystallization treatment, the solid addition product containing slurry is subjected to solid-liquid separation, and then phenol is removed from the recovered solid addition product to obtain bisphenol A.
In order to efficiently purify a large volume of reactants industrially, a continuous crystallization method has been used. In the continuous crystallization method, the solid addition product containing suspension (slurry) obtained in a crystallizer is subjected to solid-liquid separation, so that the solid addition product is recovered and the liquid phase portion remains. Since the liquid phase portion includes about 70 wt % of phenol, about 15 wt % of bisphenol A, and the remaining other by-products, the reaction mother liquid passing through a process of removing some by-products has been circulated and supplied to a reactor requiring an excessive amount of phenol, in order to recycle the phenol contained in the liquid phase portion. Furthermore, by removing phenol from the solid addition product, the bisphenol A is purified and obtained. In this process, there is a need to increase the process efficiency.